The present invention relates to microcomputers and more particularly to microcomputers constructed and enclosed so as to be suitable for use in extreme environmental conditions encountered in industrial applications.
The advent of microcomputer workstations and terminals has expanded the use of computers to a wide variety of industrial environments. Oftentimes it is desirable to locate a microcomputer workstation right in a work area of a manufacture assembly line, marine, chemical, or other industrial processing station so that the operator has access both to the computation and database resources of the microcomputer at the work site, be it a factory floor, fish processing area, chemical processing plant, or other industrial work area where the microcomputer is exposed to extreme environment conditions. These extreme operating conditions may include exposure to water, corrosive chemicals, oils, mechanical shock, vibration, wide temperature swings, and similar harsh environments that are not normally present in business office computer installations.
For example, many industrial microcomputer installations require all equipment in the work area to be hosed down periodically to clean the workstation of corrosive salt water, oils, or other chemicals.
Additionally, many industrial workstations have stringent limitations on the level of electromagnetic interference that can be tolerated. The electromagnetic emissions of any electronic or electrical equipment is therefore tightly controlled and this in turn imposes further design constraints on the enclosure used to house the industrial microcomputer.
Various efforts have been made to provide protective enclosures for microcomputers. However, partial solutions have created new problems. Tight enclosures result in extensive heat build-up within the enclosure due to the resistive losses of the electrical components, especially the heat generated by display cathode ray tubes (CRTs). Furthermore, a design of an enclosure to protect against one environmental condition often renders the microcomputer vulnerable to other extreme conditions. Further still, the protection of the microcomputer against all of the external environmental conditions must be accomplished with an enclosure that contains (suppresses) electromagnetic emissions that are inherently present in the operation of microcomputer electronics and the associated CRT display.
Added to the foregoing considerations is the need to accommodate cabling and other wiring to and from the microcomputer electronics. Where the cabling is of the flexible type common in the use of microcomputers, the difficulty of providing a sealed entry port for existing flexible cabling without the need to rewire the system through hard case conduit, has not been adequately accommodated in existing sealed computer workstations. Frequent changes of cabling must also be accommodated.
A standard keyboard readily accessible to the operator likewise needs to be sealed from environmental extremes and must contain EMI emissions.
The mechanical vibration and shock to which these industrial microcomputer units are subjected also presents severe design and engineering problems. Adequate vibration and shock protection must be provided without sacrificing the other needed features of waterproof sealing and a housing that is impermeable to most all corrosives.
The enclosure should accommodate simple and quick access to the internal components, especially the CRT display and CPU electronics, while housing both in unitary structure.